1. Field of the Invention
The invention relates to a method for structuring a surface, which comprises creating a latent structure of at least a first layer having a polymer for forming hydrophilic and hydrophobic regions by an assigned modification device for producing a printing form for offset printing.
Furthermore, the invention relates to a device for structuring a surface which comprises at least a first layer having a polymer for forming hydrophilic and hydrophobic regions by creating a latent structure of the first layer for producing a printing form for offset printing.
Printing forms whereon the surface has an outer layer of polymer material, in particular polystyrene, styrene copolymers and the like, and an inner layer of metallic material, such as aluminum, for example, have already been in use for some time in the polygraphic industry. Printing forms of this type are typically structured from an unstructured or undifferentiated state for use in offset printing for forming hydrophilic and hydrophobic regions or subregions according to the subject to be printed. A common structuring method comprises the locally selective modification of the outer layer of the surface by temporally and spatially selective exposure to the action of electromagnetic energy, in particular laser radiation, and subsequent development of the latent structure to form hydrophobic and hydrophilic regions by removal, for example using chemicals, such as for example printing-form cleaning agents, of the non-modified regions of the outer layer so that hydrophilic regions of the structure are formed for the most part by the exposed inner layer of the surface, while the modified regions of the outer layer are the hydrophobic regions of the structure.
A printing form whereon the surface can be structured by exposure to the action of thermal laser energy and subsequent chemical treatment to form hydrophilic and hydrophobic regions is disclosed, for example, in European Patent Application EP 0 931 647 A1. In addition to a polymer containing carboxyl groups, the surface, in this case, also has styrene. Furthermore, to support the absorption of laser energy, an anionic dye is provided in the surface or adjacent thereto.
In European Patent Application EP 0 931 657 A1, corresponding to U.S. Pat. Nos. 6,145,953 and 6,375,302, a method for producing an offset printing form is disclosed. After the image-related exposure of the printing form with infrared light, the image-related regions are developed by applying an aqueous liquid to the surface of the printing form. This described method can be performed, in particular, on the printing form cylinder of a printing unit or within a printing machine.
German Patent DE 44 26 012 C2 also discloses an erasing and hydrophilizing device on a printing unit in connection with erasable, i.e., regeneratable, printing forms. A cleaning fluid, an hydrophilizing agent, is sprayed either directly onto the printing form or an assigned cleaning cloth. At the circumference of the cylinder accommodating the printing form thereon, an imaging device is provided.
Conventional imaging processes for printing forms, in particular within printing units or printing machines, share a common feature that the imaging process or the structuring process is primarily based upon the interaction of light, whether by thermal or reactive effect, with the surface of the printing form. The manner wherein this is realized technically therefore requires an often sophisticated and complex imaging device, which comprises one or more light sources, in particular laser light sources. An imaging device of this type with laser light sources entails considerable costs both in procurement and in use.